Efficient key hierarchy for delivery of multimedia content

ABSTRACT

A Digital Rights Management (DRM) system provides a lightweight layering of encryption and decryption of keys that allows efficient use of different cryptographic techniques to effect the secure delivery of multimedia content. Asymmetric cryptography, where a public key is used to encrypt information that can only be decrypted by a matched private key, is used by the DRM system to deliver symmetric keys securely.

CROSS-REFERENCE

The present Application for Patent is a divisional application of U.S. application Ser. No. 11/511,736, filed Aug. 28, 2006, which claims priority to U.S. Provisional Application No. 60/714,153, filed Sep. 1, 2005, both of which are assigned to the assignee hereof and hereby expressly incorporated by reference herein.

BACKGROUND

I. Field

The following description relates generally to digital rights management and more particularly to an efficient key hierarchy for delivery of multimedia content.

II. Background

As Third Generation (3G) mobile systems and other cellular networks are deployed, new Internet Protocol (IP) packet data based services are emerging. A service area that network operators are seeking to exploit involves the distribution of video content to the mass market. High-quality video is a type of data-intensive content. Consumer experience with home viewing options provides network operators and content providers with target markets that have predefined user expectations. These user expectations combined with mobility, attractive business models, network control and management, access control, and device capabilities present complex challenges to network operators and content providers.

Protection of distributed content is a challenge that has arisen to guard against unauthorized copying and to control, either directly or indirectly, the content distribution. Content providers typically require that a content distribution system have the ability to provide Digital Rights Management (DRM), which refers to any of several technical arrangements that provide control for the user of distributed material on electronic devices with such measures installed. An underlying component for content distribution systems is the feature of encryption/decryption of media during transmission/receipt, such as in a subscription-based content distributions service. DRM software can provide the underlying encryption/decryption algorithms, hashing and authentication algorithm implementations used on both the client and the server portions. DRM can also provide license download and secure file-storage features for the client.

Two types of cryptosystems or cryptography techniques that may be utilized in DRM systems are symmetric cryptography and asymmetric cryptography. In symmetric key cryptography, the same key is used for both encryption and decryption. Examples of symmetric key cryptography include Data Encryption Standard (DES) and Advanced Encryption Standard (AES) systems. In asymmetric cryptography, also known as public-key cryptography, each user has a public key and a private key. Encryption is performed with the public key while decryption is performed with the private key. Examples of asymmetric cryptography include the Rivest, Shamir and Adleman (RSA) algorithm and Elliptic Curve Cryptography (ECC). Symmetric key cryptography is fast compared to asymmetric key cryptography, but it suffers from the drawback of having to communicate the shared keys secretly to the communicating entities. Asymmetric cryptography, as its name implies, unevenly divides processing demands based on the use of the public and private keys.

SUMMARY

The following presents a simplified summary in order to provide a basic understanding of some aspects of the disclosed embodiments. This summary is not an extensive overview and is intended to neither identify key or critical elements nor delineate the scope of such embodiments. Its purpose is to present some concepts of the described embodiments in a simplified form as a prelude to the more detailed description that is presented later.

In accordance with one or more embodiments and corresponding disclosure thereof, various aspects are described in connection with efficient key hierarchy for delivery of multimedia content. Two types of cryptographic techniques (e.g., symmetric and asymmetric cryptography) are utilized for authentication, key, and content protection. According to some embodiments, a method for performing digital rights management for a plurality of content on a client device is provided. The method includes generating an asymmetric key pair that comprises a public portion and a private portion and transmitting the public portion of the asymmetric key pair. The method also includes receiving a first symmetric key and a second symmetric key. The first symmetric key can be encrypted using the public portion of the asymmetric key pair and the second symmetric key is associated with a plurality of content.

In accordance with some embodiments is an apparatus that facilitates digital rights management. The apparatus includes a processor that executes instructions for generating an asymmetric key pair and selectively transmits at least a first portion of the asymmetric key pair to a server. A memory that stores information related to at least a second portion of the asymmetric key pair generated by the processor is also included in the apparatus.

According to some embodiments is an apparatus that facilitates data rights management of multimedia content. The apparatus includes a means for generating a public key and a private key and a means for communicating the public key to a subscription server with a request for a license file. Also included in the apparatus are a means for receiving the requested license file and a means for decrypting a multimedia content based in part on header information contained in the license file.

In accordance with some embodiments is a computer-readable medium having stored thereon computer-executable instructions for digital rights management. The instructions include generating an asymmetric key pair and sending at least a first portion of the asymmetric key pair and a request for access to multimedia content to a server. The instructions further include receiving a license file that includes symmetric keys and access information relating to the multimedia content and decrypting the access information to render the multimedia content on a display.

According to some embodiments is a processor that executes computer-executable instructions for key hierarchy for delivery of multimedia content. The instructions include generating a key pair that comprises a public key and a private key and transmitting the public key to fetch a license file from a subscription server. The instructions further include receiving license file information that includes header information and at least one symmetric key and decrypting a program based in part on the header information.

According to some embodiments is a method for performing digital rights management on a server for a plurality of content. The method includes receiving a public portion of an asymmetric key pair from a client. A first symmetric key is encrypted using a second symmetric key and is associated with a plurality of content. The second symmetric key is encrypted using the public portion of the asymmetric key pair.

In accordance with some embodiments is an apparatus that facilities delivery of multimedia content. The apparatus includes a processor that executes instructions for generating an encrypted first symmetric key and at least a second encrypted symmetric key associated with a request for delivery of multimedia content. The apparatus also includes a memory that stores information related to at least one of the first symmetric key and the at least a second symmetric key generated by the processor.

According to some embodiments is an apparatus that facilitates creation of a key hierarchy for delivery of content. The apparatus includes a means for receiving at least a portion of an asymmetric key pair from a client. Also included is a means for creating a first symmetric key and at least a second symmetric key. There is also a means for utilizing the first symmetric key to encrypt the at least a second symmetric key and a means for encrypting the second symmetric key with the at least a portion of the asymmetric key pair.

In accordance with some embodiments is a computer-readable medium having stored thereon computer-executable instructions for digital rights management. The instructions include accepting a request for access to multimedia content, the request comprising at least a portion of an asymmetric key pair. A first and at least a second symmetric key are created and the first symmetric key is encrypted with the second symmetric key pair. The instructions further include associating the second symmetric key pair with the multimedia content and sending the first symmetric key and the second symmetric key to a client.

According to some embodiments is a processor that executes computer-executable instructions for digital rights management. The instructions include generating an encrypted session key for a requested license file and creating at least one encrypted service key associated with subscribed services. The instructions further include creating at least one encrypted session key with a client encryption key and storing the encrypted service key and the at least one encrypted session key in the requested license file.

To the accomplishment of the foregoing and related ends, one or more embodiments comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative aspects and are indicative of but a few of the various ways in which the principles of the embodiments may be employed. Other advantages and novel features will become apparent from the following detailed description when considered in conjunction with the drawings and the disclosed embodiments are intended to include all such aspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a block diagram of a system for an efficient key hierarchy for delivery of multimedia content.

FIG. 2 illustrates another block diagram of a system for an efficient key hierarchy for delivery of multimedia content.

FIG. 3 illustrates an encryption of multimedia content using a program key.

FIG. 4 illustrates an encryption of the program key using a service key.

FIG. 5 illustrates an encryption of the service key using a session key.

FIG. 6 illustrates an encryption of the session key using a client encryption key.

FIG. 7 illustrates an exemplary architecture of a Digital Rights Management (DRM) system.

FIG. 8 illustrates a methodology for operation of a DRM System.

FIG. 9 illustrates a client activation call process flow.

FIG. 10 illustrates a process diagram for a client to fetch license files.

FIG. 11 shows a program decryption sequence using the various keys.

FIG. 12 illustrates a methodology for performing digital rights management on a client for a multitude of content.

FIG. 13 illustrates a methodology for performing digital rights management on a server for a multitude of content.

FIG. 14 illustrates a system for performing digital rights management on a client for a multitude of content.

FIG. 15 illustrates a system for performing digital right management on a server for a multitude of content.

FIG. 16 illustrated is a conceptual block diagram of a possible configuration of a wireless device or terminal.

GLOSSARY OF TERMS

Service Key K_(Service)=A key used to encrypt Program Keys K_(Program). Service Keys K_(Service) map to a specific service (e.g., CNN, MSNBC). Key Type: Symmetric.

Program Key K_(Program)=A key used to encrypt the video and audio data of a program. Program Keys K_(Program) map to specific programs (e.g., television programs). Key Type: Symmetric.

Session Key K_(Session)=A key used in a temporal manner to symmetrically encrypt data. A Session Key K_(Session) is used to encrypt Service Keys K_(service) in a License file. Key Type: Symmetric.

Client Encryption Key E_(Device)=The public portion of the Client encryption key. This key may be distributed to any device wanting to deliver a message to the Client. Key Type: Asymmetric.

Client Decryption Key D_(Device)=The private portion of the Client encryption key. This key remains a secret to the Client. Key Type: Asymmetric.

Authentication Key Q_(Device)=Authentication key used during Client-Server communications to authenticate each end. Key Type: keyed-Hashed Message Authentication Code.

DETAILED DESCRIPTION

Various embodiments are now described with reference to the drawings. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more aspects. It may be evident, however, that such embodiment(s) may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to facilitate describing these embodiments.

As used in this application, the terms “component”, “module”, “system”, and the like are intended to refer to a computer-related entity, either hardware, firmware, a combination of hardware and software, software, or software in execution. For example, a component may be, but is not limited to being, a process running on a processor, a processor, an object, an executable, a thread of execution, a program, and/or a computer. By way of illustration, both an application running on a computing device and the computing device can be a component. One or more components can reside within a process and/or thread of execution and a component may be localized on one computer and/or distributed between two or more computers. In addition, these components can execute from various computer readable media having various data structures stored thereon. The components may communicate by way of local and/or remote processes such as in accordance with a signal having one or more data packets (e.g., data from one component interacting with another component in a local system, distributed system, and/or across a network such as the Internet with other systems by way of the signal).

Furthermore, various embodiments are described herein in connection with a user device. A user device can also be called a system, a subscriber unit, subscriber station, mobile station, mobile device, remote station, access point, base station, remote terminal, access terminal, handset, host, user terminal, terminal, user agent, wireless terminal, wireless device, or user equipment. A user device can be a cellular telephone, a cordless telephone, a Session Initiation Protocol (SIP) phone, a wireless local loop (WLL) station, a Personal Digital Assistant (PDA), a handheld device having wireless connection capability, or other processing device(s) connected to a wireless modem.

Moreover, various aspects or features described herein may be implemented as a method, apparatus, or article of manufacture using standard programming and/or engineering techniques. The term “article of manufacture” as used herein is intended to encompass a computer program accessible from any computer-readable device, carrier, or media. For example, computer readable media can include but are not limited to magnetic storage devices (e.g., hard disk, floppy disk, magnetic strips . . . ), optical disks (e.g., compact disk (CD), digital versatile disk (DVD) . . . ), smart cards, and flash memory devices (e.g., card, stick, key drive . . . ).

Various embodiments will be presented in terms of systems that may include a number of devices, components, modules, and the like. It is to be understood and appreciated that the various systems may include additional devices, components, modules, etc. and/or may not include all of the devices, components, modules etc. discussed in connection with the figures. A combination of these approaches may also be used.

With reference now to the drawings, FIG. 1 illustrates a block diagram of a system 100 for an efficient key hierarchy for delivery of multimedia content. The various embodiments described herein provide a lightweight layering of encryption and decryption keys that provides for the efficient use of different cryptographic techniques to affect the secure delivery of multimedia content. The layering, or, hierarchy, is based on a user key encrypting a first symmetric key, which in turn encrypts a service key. The service key is used to encrypt a program key, which ultimately encrypts multimedia content.

In some embodiments, asymmetric cryptography, where a public key is used to encrypt information that can only be decrypted by a matched private key, is used to deliver symmetric keys securely. However, because of the processing differences between the two algorithms, where symmetric cryptography is computationally faster than asymmetric cryptography, once the symmetric keys are transferred symmetric cryptography is used to perform most of the encryption/decryption.

In accordance with some embodiments, symmetric cryptography is used to verify the authenticity of messages. Specifically, Hash Message Authentication Code-Secure Hash Algorithm 1 (HMAC-SHA1) can be utilized for message signing and verification. Hashing can also be used in conjunction with keys to authenticate the entities in the system 100. A hash algorithm takes as input an arbitrary length message and returns a fixed length hash value. A secure hash algorithm, which is a hash algorithm that implements a one-way function that converts the message to the fixed length value in a fashion such that the message is not easily reversible (e.g., it is not easy to go back from the hash value to the original message) is used. Further, the hashing technique used should have an extremely low probability of collisions (e.g., two different messages should not generate the same hash value). Hashing can be used in conjunction with keys to authenticate entities.

Hashing can be used with asymmetric cryptography to create Digital Signatures, which verify that an entity with the secret portion of the key encrypted a message hash and that the message was not tampered in transit. Another form of signature can be carried out with a symmetric key, such as a Message Authentication Code (MAC). A MAC can be computed with a secret key shared between sender and receiver.

System 100 can be, for example, a MediaFLO System that takes as input service content and outputs the content to a multitude of users. As discussed herein, a MediaFLO System can use both symmetric and asymmetric cryptography to protect secrets in the system. Generally, asymmetric cryptography can be used to deliver symmetric keys securely because of the processing differences between the two algorithms. Symmetric cryptography can be used to perform the bulk of the encryption/decryption. Asymmetric cryptography can be used for message authentication.

System 100 may be included in a client or user device 102 that can be a mobile device, such as a cellular phone, smart phone, laptop, handheld communication device, handheld computing devices, satellite radios, global positioning system, Personal Digital Assistants (PDA), and/or other suitable devices for communicating over a wireless communication network. The user device 102 can communicate wirelessly with a license management server 104. Although a number of user devices(s) 102 and servers(s) 104 can be included in a communication network, as will be appreciated, a single user device 102 that transmits communication data signals with a single server 104 is illustrated for purposes of simplicity.

User device 102 can include a processor 106 that can be configured to generate a key pair 108, such as an asymmetric key pair. The key pair 108 can include a public portion and a private portion. The asymmetric key pair can be generated during an activation process, for example, which will be discussed in more detail below. The public portion of the key pair 108 can be transmitted (e.g., wirelessly), by transmitter/receiver 110 to server 104 to obtain digital rights to a multimedia content and/or to fetch a license file from a license server 104. Digital rights can describe how the content may be used on a device. For example, the Digital rights associated with the content may restrict just viewing of the content, viewing of the content for a specified number of timers, permissible saving on the content, time(s) when the content can be viewed, and so forth. It should be understood that although a transmitter/receiver is illustrated as one component, it could be configured with two or more components.

If user device 102 is authorized to obtain the multimedia content, server can respond with one or more symmetric keys 114, which can be received by device's transmitter/receiver 110. A storage media 112 can be configured to maintain information associated with the asymmetric keys 108, the symmetric keys 114, or both types of keys in a retrievable format. For example, a first symmetric key received at user device 102 can be encrypted using the public portion of the key pair 108. In some embodiments, the first symmetric key can be encrypted with a decryption scheme that can be associated with a validation period after which the key is rendered inactive (or another deactivation scheme). A second symmetric key received can be associated with a plurality of content (e.g., multimedia content). In some embodiments, the second symmetric key can be encrypted with the first symmetric key.

Processor 110 can be configured to decrypt the symmetric keys. For example, the first symmetric key can be decrypted utilizing the private portion of the asymmetric key pair 108. In accordance with some embodiments, the first and second symmetric keys 114 are included in a license file 116. In such embodiments, processor 110 can be configured to retrieve the second symmetric key from the license file and decrypt it based on the first symmetric key using symmetric cryptography. A display 118 can be associated with user device 102 and decrypting the program can be performed at substantially the same time as media is rendered on a display.

In accordance with some embodiments, a third symmetric key can be provided by server 104 and can be associated with a first content in the multitude of multimedia content and the second symmetric key. The processor 110 can be configured to decrypt the third symmetric key utilizing the second symmetric key and to decrypt the first content from the multitude of content associated with the third symmetric key. In some embodiments, the third symmetric key can be encrypted (and decrypted) with the first symmetric key.

In addition or alternatively, receiver 110 can be configured to receive license file 116 information that includes header information (e.g., User ID, EpochID). The license file 116 may also include an encrypted session key and at least one service key. The encrypted service key can be stored in a retrievable format in a storage media 112. Processor 110 can be configured to decrypt a program or multimedia content based in part on the header information received in license file 116. The decryption can occur, in accordance with some embodiments, at substantially the same time as the program or multimedia content is rendered on display 118.

Any reference to memory, storage, database, or other medium as used herein can include nonvolatile and/or volatile memory. Suitable nonvolatile memory can include read only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory can include random access memory (RAM), which acts as external cache memory. By way of illustration and not limitation, RAM is available in many forms such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), Synchlink DRAM (SLDRAM), Rambus direct RAM (RDRAM); direct Rambus dynamic RAM (DRDRAM), and Rambus dynamic RAM (RDRAM).

FIG. 2 illustrates another block diagram of a system 200 for an efficient key hierarchy for delivery of multimedia content. System includes one or more clients or user devices 202 (e.g., mobile device) and one or more servers 204, which can be a license server or an authentication device. User device 202 can be configured to generate an asymmetric key pair 206, which can include a private portion 208 and a public portion 210. The public portion 210 of the key pair 206 can be transmitted to server 204 to obtain rights to multimedia content on user device 202 to which a user of user device 202 has subscribed.

Server 204 can be configured to receive public portion 210 from user device 202, such as by a receiver 212 (shown as a transmitter/receiver 212 pair). Server 204 can also be configured to receive or request (from user device 202 or another source at least one service identifier 214 that can be associated with content 216 subscribed to by user of user device 202.

A processor 218 associated with server 204 can be configured to generate various symmetric keys that can be utilized by user device 202 to obtain access to multimedia content. For example, processor 218 can generate a first and a second symmetric key 220 and encrypt the first symmetric with the second symmetric key. The second symmetric key can be encrypted using the public portion 208 of the asymmetric key pair 206. In accordance with some embodiments, the first symmetric key is associated with content 216 subscribed to by a user. To encrypt the first symmetric key, processor 218 can be configured to retrieve one or more service identifiers 214 associated with content 216 subscribed to by user and the second symmetric key based on the retrieved one or more service identifiers 214. In accordance with some embodiments, client can be authenticated by server 204 or another device before encryption of the symmetric keys. Symmetric keys 220 can be communicated to user device by transmitter 212.

In accordance with some embodiments, server 204 receives a request for a license file 222 from user device 202. The request can included a client encryption key 208 and a list of subscribed services 214. Processor 218 can be configured to generated an encrypted session key 220 associated with the subscribed services 214 (by symmetric cryptography) and an encrypted session key 220 that is encrypted with the client encryption key 208 (by asymmetric cryptography). A storage media 224 associated with server 204 (or processor 218) can store or maintain the encrypted service key and the at least one encrypted session key in the requested license file 222. The license file 222 can be sent to the authenticated user device 202.

FIG. 3 illustrates an encryption 300 of multimedia content using a program key. The multimedia content for a specific program (cleartext program 302) is encrypted using symmetric cryptography using symmetric key encryption 304 by a Program Key K_(Program) 306. Cleartext is the name given to data before a cipher operation is applied to it and ciphertext is the name given to data after a cipher operation has been applied. The Program Key K_(Program) 306 is itself encrypted by Service Key K_(Service) (not shown) and the encrypted Program Key K_(Program) 306 is delivered along with the program K_(Program)[Program] 308. The programming can include a metadata portion and a content portion. The content portion is encrypted by the Program Key K_(Program) 306. The metadata portion of the programming, which includes information about the content portion (e.g., digital representation of the content, the security or rights management information, and so on), includes the encrypted Program Key K_(Program) 306.

With reference now to FIG. 4 illustrated is an encryption 400 of the program key using a service key. The Program Key K_(Program) 402 is encrypted by a respective Service Key K_(Service) 404 using symmetric key encryption 406. This produces an Encrypted Program Key (K_(Service)[K_(Program)]) 408. By protecting each Program Key K_(Program) 402 using its respective Service Key K_(Service) 404, a single program can be reused for different services and the Program Keys used to encrypt the program for the different services are the only data that should be duplicated.

For exemplary purposes and not limitation, a first user “A” subscribes to the ESPN service, and a second user “B” subscribes to both the CNN service and the ESPN service. A program that is to be “aired” on both services, for example a commercial advertisement (Ad) program, is encrypted using an Ad Program Key K_(ProgramAd) to create an encrypted Ad program K_(ProgramAd)(Ad Program). The Ad Program Key K_(ProgramAd) is encrypted by an ESPN Service Key K_(ServiceESPN) to create an ESPN service encrypted Ad Program Key K_(ServiceESPN)(K_(ProgramAd)). The Ad Program Key K_(ProgramAd) is also encrypted by a CNN Service Key K_(ServiceCNN) to create a CNN service encrypted Ad Program Key K_(ServiceCNN)(K_(ProgramAd)). The ESPN service encrypted Ad Program Key K_(ServiceESPN)(K_(ProgramAd)) is distributed to the first user A and the second user B along with encrypted Ad Program K_(ProgramAd)(Ad Program). The first user A and the second user B can access the Ad Program in the ESPN service after the K_(ProgramAd) is retrieved by using the ESPN Service Key K_(ServiceESPN). However, because the same key (K_(ProgramAd)) is used to encrypt the Ad program, the Ad program is also accessible by the second user B through the CNN service without having to distribute another copy of the encrypted Ad program for the CNN service K_(ProgramAd)(Ad Program). Only the CNN service encrypted Ad Program Key K_(ServiceCNN)(K_(ProgramAd)) Should be distributed. Thus, the Ad Program can be decrypted second user B whether the user is accessing the ESPN service (by retrieving/decrypting the Ad Program Key K_(ProgramAd) from the ESPN service encrypted Ad Program Key K_(ServiceESPN)(K_(ProgramAd))), or the CNN service (by retrieving/decrypting the Ad Program Key K_(ProgramAd) from the CNN service encrypted Ad Program Key K_(ServiceCNN)(K_(ProgramAd))).

FIG. 5 illustrates an encryption 500 of the service key using a session key. The Service Key K_(Service) 502 is encrypted by the Session Key KSession 504 using symmetric key encryption 506 to create an Encrypted Service Key (K_(Session)[K_(Service)]) 508. In some embodiments, the Session Key K_(Session) 504 covers multiple Service Keys K_(Service) 502, where the multiple Service Keys K_(Service) 502 are delivered in a License File 510. Thus, the service provided to a particular user, which can be based on the services subscribed to by the user, is defined by the License File 510. In addition, each License File 510 and the Service Keys K_(Service) 502 in the License File 510 can be valid for some predetermined time period, which can be referred to as an “Epoch.” After such predetermined time period, the License File 510 and the Service Keys K_(Service) 502 in the License File 510 are expired or rendered invalid. The expiration of such keys can contain or mitigate system damage that may be a result of a key become known to an unauthorized user. Service Keys for a given epoch should be removed from the device after the expiration time of content for which a viewing time has been defined in a given epoch.

Although Service Keys K_(Service) may be encrypted by asymmetric encryption using Client Encryption Key E_(Device), this method of encryption (and its associated method of decryption) can be slow. Thus, a Session Key K_(Session) can be created for each Client/License/Epoch and only the Session Key K_(Session) is protected using asymmetric cryptography. For decryption of the Service Keys K_(Service) to be fast on the Client so that the presentation of the “channels” that is being selected by the user is fast (e.g., the decryption of the particular program key needed to decrypt the program associated with the service selected by the user as the user is “channel surfing” should be fast), all Service Keys K_(Service) are protected by the single Session Key K_(Session) for that Epoch, which implements symmetrical cryptography to protect the Service Keys K_(Service). In this manner, Service Keys K_(Service) are protected as long as possible as they are stored in encrypted form on the Client using symmetric cryptography. In some embodiments, the encrypted Session Key K_(Session) is decrypted (using asymmetric cryptography) at substantially the same time as the client is activated, and the decrypted Session Key K_(Session) is cached on the client so that it may be used to decrypt one or more Service Keys K_(Service) (using symmetric cryptography, which is comparably faster than asymmetric cryptography) without having to be decrypted each time.

FIG. 6 illustrates an encryption 600 of the session key using a client encryption key. The Session Key K_(Session) 602 is encrypted by the Client's or Device's Encryption Key E_(Device) 604, which is a public key, for delivery to the Client using an Asymmetric Key Encryption 606. The Encrypted Session Key (E_(Device)[K_(Session)]) is delivered and the Client can decrypt Session Key K_(Session) 602 using the Client's Decryption Key D_(Device), which is a private key.

With reference now to FIG. 7 illustrated is an exemplary architecture of a Digital Rights Management (DRM) system 700. In some embodiments, the layering, or, hierarchy, of the different types of keys is based on a Client Encryption Key E_(Device) encrypting a Session Key K_(Session), which in turn encrypts a Service Key K_(Service). Further, the Service Key K_(Service) is used to encrypt a Program Key K_(Program) that is used to protect multimedia content. Thus, the DRM system 700 described herein can employ a hierarchy of keys to protect the digital rights of the content. In some embodiments, Advanced Encryption Standard-Counter (AES-CTR) is used as the symmetric key algorithm, where AES is the cryptographic standard adopted by the National Institute of Standards and Technology (NIST) as US Federal Information Processing Standards (FIPS) PUB 197.

Included in DRM system 700 is a Client 702 (representative of all clients that may be present in system 700), a DRM Server 704, a License Key Server 706, and a Subscription Server 708. In some embodiments, a suite of cryptographic and DRM system modules provides the underlying encryption/decryption and hashing/authentication components to be used at Client 702, DRM Server 704, License Key Server 706, and Subscription Server 708. In addition, the suite of cryptographic and DRM system modules can also provide the license retrieval/download features and secure file-storage features for Client 702, such storage can be associated with a client key database 710.

The functionality provided by the suite of cryptographic and DRM system modules may be broken up into different general categories that can include Public Key Cryptography functionality, Media Cipher functionality, and Authentication functionality. The different categories of functionality interact with one another to provide such functionality as secure file storage, random number generation (RNG), retrieval and storage of keys in an embedded file system (EFS). For example, the Authentication functionality provides the functionality to generate authentication keys, and sign and verify messages at the clients and servers using an authentication key. The Authentication functionality also provides the functionality to store the authentication key in the EFS and retrieve it when needed on Client 702.

In some embodiments, the algorithm used for signing and verification is the HMAC, keyed-hash algorithm, which in some embodiments uses authentication keys in conjunction with Message-Digest version 5 (MD5) hash algorithm to generate the message authentication code. For example, the Authentication key Q_(Device) that is used during client/server communications is a keyed-Hash Message Authentication Code (HMAC), which is a type of message authentication code calculated using a cryptographic hash function in combination with a secret key. As with any MAC, the code may be used to verify both the data integrity and the authenticity of a message at substantially the same time. Any iterative cryptographic hash function, such as Message-Digest algorithm 5 (MD5) or Secure Hash Algorithm 1 (SHA-1), may be used in the calculation of an HMAC; with the resulting MAC algorithm being termed HMAC-MD5 or HMAC-SHA-1, accordingly. The cryptographic strength of the HMAC depends upon the cryptographic strength of the underlying hash function and on the size and quality of the key.

The Media Cipher category of functionality provides functionality to generate Program Keys K_(Program), Service Keys K_(Service), and Session Keys K_(Session), and encrypt and decrypt media and keys using these keys. In some embodiments, the functionality is provided by a cryptography core. All encryption and decryption functions, except for the encryption/decryption of Session Keys K_(Session), can be performed using symmetric cryptography. As discussed herein, the encryption/decryption of Session Keys K_(Session) can be performed using asymmetric cryptography.

Client 702 can generate a public/private key pair as part of an activation process. In some embodiments, the Public Key Cryptography and Authentication categories of functionally are used during a client activation call process, which is the process by which Client 702 registers itself with the servers in DRM system 700. A client activation call process will be discussed in more detail below with reference to FIG. 9.

FIG. 8 illustrates a methodology 800 for operation of a DRM System. At 802, a public/private key pair is generated. Such generation of the key pair can occur at substantially the same time as the Client is activated and the key pair can be stored on Client. The public key can also be communicated to a Subscription Server. Client may be thought of as the owner of a cryptographic identity through the generation of the public/private key pair. As described herein, the provision of the public key provides a secure channel of communication to Client. Specifically, Public Key Cryptography functionality provides the functionality to generate the Client Encryption Key E_(Device) and Client Decryption Key D_(Device) and stores the keys on Client. In some embodiments, the Client Encryption Key E_(Device) is a public key and the Client Decryption Key D_(Device) is a private key, and these keys comprise a public/private key pair. Thus, the activation process causes these keys to be generated, placed in the EFS and causes the public portion of the Client Key E_(Device) to be populated in a Client Key Database on a Subscription Server.

At 804, Client can contact Subscription Server by sending its Public Key E_(Device) and Subscription Server can send the key to a license server to update Client Key Database. This public portion of the key pair is later used for encrypting the license files or other secret information sent to Client. The activation process also causes a user identifier (UserID) to be assigned to Client. The Client Encryption Key E_(Device) of Client is associated with this particular UserID. In some embodiments, all further communication of Client with License Key Server uses this UserID to retrieve the correct licenses.

After or at substantially the same time as Client has been authenticated, Subscription Server sends a request to DRM server for an Authentication Key Q_(Device) for Client. DRM Server generates the Authentication Key Q_(Device) and returns it to Subscription Server. Subscription Server encrypts the Authentication Key Q_(Device) with E_(Device) and it sends the encrypted Authentication Key E_(Device)(Q_(Device)) back to Client. Client, after authenticating the server, stores the encrypted Authentication Key E_(Device) (Q_(Device)) into the EFS of Client. Client and the servers now share an authentication key that can be used to authenticate messages from each other. Once Client has been activated, the License file needed to access the services in DRM System may be obtained by Client. In some embodiments, a new License file containing a new set of Service Keys and K_(Service) are obtained at predetermined intervals (e.g., expiration of an Epoch) in order for Client to continue to access the media content.

At 806, License Key Server is contacted by Client for fetching a License file. A process diagram for Client to fetch License Files will be described below with reference to FIG. 10. Once obtained, the License File can be stored locally in Client for later retrieval of the Service Keys K_(Service) and Session Key K_(Session) stored therein. To process the request, at 808, License Key Server can determine if Client is an authentic and authorized Client by contacting a Subscription Server and retrieving the Client Encryption Key E_(Device) and Authentication Key Q_(Device) of Client in addition to a list of services that are subscribed to by Client (ServiceIDs) based on the UserID. Thus, Subscription Server provides client authentication information in the form of the Authentication Key Q_(Device) of Client. Once these keys are retrieved, License Key Server can check the signature using the Client Encryption Key E_(Device) of Client.

If Client is authenticated, then the request for the License file is passed to DRM server. Thus, DRM server is only contacted after Client is authenticated and authorized. Specifically, at 810, the Client Encryption Key E_(Device) of Client and the list of services subscribed to by Client are sent to DRM Server. DRM Server will generate the Session Key K_(Session) for the License File and encrypt all Service Keys K_(Service) for the services subscribed to by Client, as determined by the ServiceIDs, using the Session Key K_(Session). The encryption of the Service Keys. K_(Service) is performed by symmetric cryptography. DRM Server will also encrypt the Session Key K_(Session) using the Client Encryption Key E_(Device) of Client. As discussed above, this encryption is performed using asymmetric cryptography.

At 812, the encrypted Session Key K_(Session) and the encrypted Service Keys K_(Service) are stored in the License File by License Key server, along with other header information such as the UserID, EpochID for which the Service Keys K_(Service) are valid, and the Epoch start and, end times. Thus, it should be noted that multiple License Files may be generated for a client in a predetermined time period, and each License File can contain the Service Keys K_(Service) that are valid for that particular Epoch, with the Service Keys K_(Service) being encrypted with the Session Key K_(Session) generated for that License File. For example, when a user changes a subscription, Client, should acquire a changed set of Service Keys K_(Service) associated with the changed, subscribed programming. This changed set of Service Keys K_(Service) is delivered with a new License File that includes a newly generated (and encrypted) Session Key K_(Session).

An exemplary License file is shown below:

License Header: UserID, EpochID, Epoch Start and End Time E_(Device) (K_(Session)) K_(Session) (K_(Service1)) User rights for Service 1 K_(Session) (K_(Service2)) User rights for Service 2 . . . K_(session) (K_(ServiceN)) User rights for Service N Signature on the license.

At 814, the License file is sent back to Client by License Key server. In some embodiments, the ultimate result is to provide Client with License File (including the multiple Service Keys K_(Service)) and the Session Key K_(Session) (for the Epoch) secured as discussed above.

At 816, to decrypt a program, Client uses the EpochID, ServiceID, ProgramID and encrypted Program Key K_(Program) in the function call to fetch the Key to obtain a decrypted Program Key K_(Program). For example, given an EpochID Y, a ServiceID X, ProgramID Z and an encrypted Program Key K_(ServiceX) (K_(ProgramZ)), a decrypted Program Key K_(ProgramZ) can be obtained. A program decryption sequence will be described below with reference to FIG. 11.

At 818, Client decrypts and plays the media content. In some embodiments, the actual symmetric cryptography decryption of the content using the Program Key K_(Program) occurs at substantially the same time as the media is being rendered on the display through a player on Client. The encrypted program file name and the Program Key K_(Program) are then fed to the player using the interface. The media decryption can use a virtual file I/O interface that provides a virtual file I/O wrapper around the cryptography core implementation and simplifies the decryption process to the player.

FIG. 9 illustrates a client activation call process flow 900. Public Key Cryptography functionality can provide the functionality to generate Client keys and encrypt and decrypt Session keys using Client keys. In some embodiments, Public Key Cryptography functionality also provides wrapper functions to decrypt encrypted Program keys and to cache a Session key for a particular Epoch. In some embodiments, Client keys are generated using an algorithm based on one described by Ron Rivest, Adi Shamir and Len Adleman (RSA), having both a public key and a private key.

DRM Client 902 communicates a Client Encryption Key E_(Device) to a subscription server 904 through a Phone Info Hash 906, for example. Subscription Server 904 can authenticate Device, at 908, and forward Client Encryption Key E_(Device) to a DRM Server 910, at 912 at substantially the same time as Client 902 is authenticated. DRM Server 910 replies, at 914, with the Client Encryption Key associated with an Authentication Key E_(Device)(Q_(Device)) and the Authentication Key Q_(Device). The Client Encryption Key associated with an Authentication Key E_(Device)(Q_(Device)) and Phone Info Hash are sent, at 916, to DRM Client 902.

A process diagram 1000 for Client to fetch License files is illustrated in FIG. 10. In some embodiments, DRM Client 1002 fetches License files from License Key Server 1004 by providing the License Key Server with the identification of the user (e.g., UserID) and the identification of the epoch (e.g., EpochID) for which Client 1002 desires to fetch the License file. The user identification and epoch are sent, at 1006, with the license request. In addition, Client 1002 can provide License Key Server 1004 with the Authorization Key Q_(Device) of Client 1002 signed using the Client Decryption Key D_(Device) of Client 1002.

License Key Server 1004 requests client authentication from Subscription Server 1008, at 1010. Subscription Server 1008 can respond to the request for Client Authentication (e.g., Service IDS, E_(Device), Q_(Device)), at 1012. Client 1002 is authenticated, at 1014, and a request for service keys (e.g., Service IDS, EpochID, E_(Device)) is sent to DRM Server 1016, at 1018.

Encrypted Session Key K_(Session) and encrypted Service Keys K_(Service) are generated, at 1020, by Server 1016. At 1022, a response to the request for service keys (encrypted Session Key K_(Session), encrypted Service Keys K_(Service)) is sent to License Key Server 1004. A response to the request for license is sent, at 1024, to Client 1002. Once obtained, the License file can be stored, at 1026, locally in Client 1002 for later retrieval of the Service Keys K_(Service) and Session Key K_(Session) stored therein.

FIG. 11 illustrates a program decryption sequence 1100 using the various keys, where, internally, Client assumes that the License required for the Epoch associated with EpochID has already been fetched. At 1102, Client uses the previously stored Client Decryption Key D_(Device) to decrypt the Session Key E_(Device)(K_(Session)) in the License File, the decrypted (ClearText) Session Key K_(Session) to decrypt the Service key for Service X K_(Session)(K_(ServiceX)) in the License file, at 1104, and the decrypted Service key for Service X K_(ServiceX) to decrypt the encrypted Program key for Program Z K_(ServiceX)(K_(ProgramZ)), at 1106. It then returns the Program Key K_(ProgramZ) in the clear for decryption of the Program, at 1108. Thus, in some embodiments, in order to decrypt the program at Client, Client assumes that the user is activated within the system and has the proper client key files (e.g., the Client Encryption Key E_(Device) and the Client Decryption Key D_(Device)). It also assumes that the License File for the particular Epoch has been downloaded to Client. Should these requirements not hold true, DRM system can report errors. Should different key files (other than the ones generated when Client was activated within the system) be present on Client the decryption will take place without errors but the output data will be not be useful data.

A methodology 1200 for performing digital rights management on a client for a multitude of content is illustrated in FIG. 12. While, for purposes of simplicity of explanation, the methodologies disclosed herein are shown and described as a series of blocks, it is to be understood and appreciated that the claimed subject matter is not limited by the number or order of blocks, as some blocks may occur in different orders and/or concurrently with other blocks from what is depicted and described herein. Moreover, not all illustrated blocks may be required to implement the methodologies described hereinafter. It is to be appreciated that the functionality associated with the blocks may be implemented by software, hardware, a combination thereof or any other suitable means (e.g. device, system, process, component). Additionally, it should be further appreciated that the methodologies disclosed throughout this specification are capable of being stored on an article of manufacture to facilitate transporting and transferring such methodologies to various devices. Those skilled in the art will understand and appreciate that a methodology could alternatively be represented as a series of interrelated states or events, such as in a state diagram.

Method 1200 starts, at 1202, where an asymmetric key pair is generated, for example, as part of an activation process. Generation of the asymmetric key pair may include generating a public key or public portion and a private key or private portion. At 1204, a public portion of the asymmetric key pair is transmitted to a server, digital rights management authority, license server, or the like (refereed to herein as server). The server can encrypt a first symmetric key and a second symmetric key and transmit the encrypted symmetric keys to the client. At 1206, the first symmetric key and second symmetric key are received at the client.

A first symmetric key may be encrypted using a public portion of the asymmetric key pair. In some embodiments, the first symmetric key may be encrypted with a decryption scheme that is valid for predetermined interval (e.g., time, or other scheme for measuring an interval). A second symmetric key can be associated with a multitude of content. In some embodiments, the second symmetric key can be encrypted with the first symmetric key.

In some embodiments, method 1200 can continue, at 1208, where the first symmetric key, the second symmetric key, or both symmetric keys are decrypted. For example, the first symmetric key may be decrypted using the private portion of the asymmetric key pair. If the second symmetric key is encrypted with the first symmetric key, decryption of the second symmetric key may be based on the first symmetric key.

Receiving a third symmetric key, at 1210, can be included in method 1200 in accordance with some embodiments. The third symmetric key can be associated with the multitude of content. The server can encrypt the third symmetric key with the first symmetric key. Method 1200 continues, at 1208, where at least the third symmetric key is decrypting based on the first symmetric key.

In accordance with some embodiments, the first symmetric key and the second symmetric key may be contained in a license file. If contained in a license file, decrypting the second symmetric key that is based on the first symmetric key, at 1208, includes retrieving the second symmetric key from the license file and decrypting the second symmetric key using symmetric cryptography. In some embodiments, a first content in a multitude of content and the second symmetric key are associated with a third symmetric key. The third symmetric key can be decrypted using the decrypted second symmetric key and the first content can be decrypted from the multitude of content associated with the third symmetric key.

FIG. 13 illustrates a methodology 1300 for performing digital rights management on a server for a multitude of content. Method 1300 starts at 1302, where a public portion of an asymmetric key pair is received from a client. At 1304, a first symmetric key is encrypted using a second symmetric key. The first symmetric key can be associated with a multitude of content. Encrypting the first symmetric key can include retrieving a multitude of service identifiers (IDs) associated with a multitude of content subscribed to by the client. The first symmetric key can be retrieved based on the retrieved multitude of service IDs. In some embodiments, before encrypting the first symmetric key, the client is authorized, at 1306. The method 1300 continues at 1308, where the second symmetric key is encrypted using the public portion of the asymmetric key pair. In accordance with some embodiments, the first and second symmetric keys can be transmitted to the client, at 1310.

With reference now to FIG. 14, illustrated is a system 1400 for performing digital rights management on a client for a multitude of content. System 1400 is represented as functional blocks, which can be functional blocks that represent functions implemented by a processor, software or combination thereof (e.g., firmware).

System 1400 includes a generating module 1402 that can be configured to generate a public key and a private key. The keys can be generated utilizing asymmetric cryptography. Also included is a communicating module 1404 that can be configured to communicate the public key to a license server with a request for a license file. A receiving module 1406 can be configured to receive the requested license file. The license file can be received from a server, for example. Also included is a decrypting module 1408 that can be configured for decrypting a multimedia content based in part on header information contained in the license file. In accordance with some embodiments, system 1400 can also include a storage module (not shown) that can be configured to store a service key contained in the license file. In accordance with some embodiments a rendering module (not shown) that can be configured to render a media on a display screen at substantially a same time as the multimedia content is decrypted in included in system.

FIG. 15 illustrates a system 1500 for performing digital right management on a server for a multitude of content. System 1500 is represented as functional blocks, which can be functional blocks that represent functions implemented by a processor, software or combination thereof (e.g., firmware).

System 1500 includes a receiving module 1502 that can be configured to receive at least a portion of an asymmetric key pair from a client. The received portion can be a public portion. Also included is a creating module 1504 that can be configured to create a first symmetric key and at least a second symmetric key. The first symmetric key can be associated with a plurality of content. System 1500 can further include a utilizing module 1506 that can be configured to utilize the first symmetric key to encrypt the at least a second symmetric key. Also included is an encrypting module that can be configured to encrypt the second symmetric key with the at least a portion of the asymmetric key pair. In accordance with some embodiments is an authentication module (not shown) that can be configured to authenticate a client before creating the first symmetric key and the at least a second symmetric key. In accordance with some embodiments is a transmitting module (not shown) that can be configured to transmit the encrypted first symmetric key and encrypted second symmetric key to a client.

With reference now to FIG. 16, illustrated is a conceptual block diagram of a possible configuration of a wireless device or terminal 1600. As those skilled in the art will appreciate, the precise configuration of the terminal 1600 may vary depending on the specific application and the overall design constraints. Processor 1602 can implement the systems and methods disclosed herein.

Terminal 1600 can be implemented with a front-end transceiver 1604 coupled to an antenna 1606. The front-end transceiver 1604 is configured to receive a data communication. A base band processor 1608 can be coupled to the transceiver 1604. The base band processor 1608 can be implemented with a software-based architecture, or other types of architecture. A microprocessor can be utilized as a platform to run software programs that, among other functions, provide control and overall system management function. A digital signal processor (DSP) can be implemented with an embedded communications software layer, which runs application specific algorithms to reduce the processing demands on the microprocessor. The DSP can be utilized to provide various signal processing functions such as pilot signal acquisition, time synchronization, frequency tracking, spread-spectrum processing, modulation and demodulation functions, and forward error correction.

Terminal 1600 can also include various user interfaces 1610 coupled to the base band processor 1608. User interfaces 1610 can include a keypad, mouse, touch screen, display, ringer, vibrator, audio speaker, microphone, camera, and/or other input/output devices.

The base band processor 1608 comprises a processor 1602. In a software-based implementation of the base band processor 1608, the processor may be a software program running on a microprocessor. However, as those skilled in the art will readily appreciate, the processor 1602 is not limited to this embodiment, and may be implemented by a variety of means known in the art, including hardware configurations, software configuration, or combination thereof, which is capable of performing the various functions described herein. The processor 1602 can be coupled to memory 1612 for the storage of data. The memory 1612 is configured to store the program data received during a manufacturing and/or test process and the processor 1602 or 1608 is configured to be programmed with the program data.

The various embodiments (e.g., in connection with efficient key hierarchy for delivery of multimedia content and digital rights management) can employ various AI-based schemes for carrying out various aspects thereof. For example, a process for validating and invalidating various keys for one or more user through an automatic classifier system and process. As used herein, the term “inference” refers generally to the process of reasoning about or inferring states of the system, environment, and/or user from a set of observations as captured through events, sensors, and/or data. Inference can be employed to identify a specific context or action, or can generate a probability distribution over states, for example. The inference can be probabilistic—that is, the computation of a probability distribution over states of interest based on a consideration of data and events. Inference can also refer to techniques employed for composing higher-level events from a set of events and/or data. Such inference results in the construction of new events or actions from a set of observed events and/or stored event data, whether or not the events are correlated in close temporal proximity, and whether the events and data come from one or several event and data sources. Various classification schemes and/or systems (e.g., support vector machines, neural networks, expert systems, Bayesian belief networks, fuzzy logic, data fusion engines . . . ) can be employed in connection with performing automatic and/or inferred action in connection with the subject embodiments.

A classifier is a function that maps an input attribute vector, x=(x1, x2, x3, x4, xn), to a confidence that the input belongs to a class, that is, f(x)=confidence(class). Such classification can employ a probabilistic and/or statistical-based analysis (e.g., factoring into the analysis utilities and costs) to prognose or infer an action that a user desires to be automatically performed.

A support vector machine (SVM) is an example of a classifier that can be employed. The SVM operates by finding a hypersurface in the space of possible inputs, which hypersurface attempts to split the triggering criteria from the non-triggering events. Intuitively, this makes the classification correct for testing data that is near, but not identical to training data. Other directed and undirected model classification approaches include, e.g., naïve Bayes, Bayesian networks, decision trees, neural networks, fuzzy logic models, and probabilistic classification models providing different patterns of independence can be employed. Classification as used herein also is inclusive of statistical regression that is utilized to develop models of priority.

As will be readily appreciated from the subject specification, the one or more embodiments can employ classifiers that are explicitly trained (e.g., through a generic training data) as well as implicitly trained (e.g., by observing user behavior, receiving extrinsic information). For example, SVM's are configured through a learning or training phase within a classifier constructor and feature selection module. Thus, the classifier(s) can be used to automatically learn and perform a number of functions, including but not limited to determining according to a predetermined criteria when to create keys, which types of keys to create, etc. The criteria can include, but is not limited to, the amount of data or content to access, the type of content, the importance of the content, etc.

It is to be understood that the embodiments described herein may be implemented by hardware, software, firmware, middleware, microcode, or any combination thereof. When the systems and/or methods are implemented in software, firmware, middleware or microcode, program code or code segments, they may be stored in a machine-readable medium, such as a storage component. A code segment may represent a procedure, a function, a subprogram, a program, a routine, a subroutine, a module, a software package, a class, or any combination of instructions, data structures, or program statements. A code segment may be coupled to another code segment or a hardware circuit by passing and/or receiving information, data, arguments, parameters, or memory contents. Information, arguments, parameters, data, etc. may be passed, forwarded, or transmitted using any suitable means including memory sharing, message passing, token passing, network transmission, etc.

For a software implementation, the techniques described herein may be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. The software codes may be stored in memory units and executed by processors. The memory unit may be implemented within the processor or external to the processor, in which case it can be communicatively coupled to the processor through various means as is known in the art.

The disclosed embodiments may be applied to any one or combinations of the following technologies: Code Division Multiple Access (CDMA) systems, Multiple-Carrier CDMA (MC-CDMA), Wideband CDMA (W-CDMA), High-Speed Downlink Packet Access (HSDPA), Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, and Orthogonal Frequency Division Multiple Access (OFDMA) systems.

The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor, such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal.

It should be noted that the methods described herein may be implemented on a variety of hardware, processors and systems known by one of ordinary skill in the art. For example, the general requirement for the client to operate as described herein is that the client has a display to display content and information, a processor to control the operation of the client and a memory for storing data and programs related to the operation of the client. In some embodiments, the client is a cellular phone. In some embodiments, the client is a handheld computer having communications capabilities. In yet another embodiment, the client is a personal computer having communications capabilities. In addition, hardware such as a GPS receiver may be incorporated as necessary in the client to implement the various embodiments described herein. Further, although terms such as “client” and “server” has been used herein to refer to specific devices and/or entities, these terms should not be construed to be limiting in anyway but are used to provide a clearer explanation of the embodiments contained herein. Thus, a device or entity that is a “client” in one sequence of transaction or scenario may be considered a “server” in another sequence of transactions or scenario.

The various illustrative logics, logical blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but, in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

What has been described above includes examples of one or more embodiments. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the aforementioned embodiments, but one of ordinary skill in the art may recognize that many further combinations and permutations of various embodiments are possible. Accordingly, the described embodiments are intended to embrace all such alterations, modifications and variations that fall within scope of the appended claims. Furthermore, to the extent that the term “includes” is used in either the detailed description or the claims, such term is intended to be inclusive in a manner similar to the term “comprising” as “comprising” is interpreted when employed as a transitional word in a claim. 

What is claimed is:
 1. An apparatus that facilitates data rights management of multimedia content, comprising: means for generating, by a hardware processor, a public key and a private key; means for communicating the public key to a subscription server with a request for a license file; means for receiving the requested license file; and means for decrypting a multimedia content based in part on header information contained in the license file, the header information including a User Identification and an Epoch Identification, wherein the Epoch Identification defines a time period for which the license file is valid.
 2. The apparatus of claim 1, further comprising means for storing a service key contained in the license file.
 3. The apparatus of claim 1, further comprising means for rendering a media on a display screen at substantially a same time as the multimedia content is decrypted.
 4. A non-transitory computer-readable medium having stored thereon computer executable instructions for digital rights management, the instructions comprising: generating an asymmetric key pair; sending at least a first portion of the asymmetric key pair and a request for access to multimedia content to a server; receiving a license file that includes symmetric keys relating to the multimedia content and header information including a User Identification and an Epoch Identification, wherein the Epoch Identification defines a time period for which the license file is valid; and decrypting the multimedia content based in part on the header information contained in the license file.
 5. The computer-readable medium of claim 4, the instructions further comprising maintaining a second portion of the asymmetric key pair in a storage media.
 6. The computer-readable medium of claim 4, the first portion of the asymmetric key pair is a public key and the second portion of the asymmetric key pair is a private key.
 7. A processor that executes computer-executable instructions from a non-transitory computer medium for key hierarchy for delivery of multimedia content, the instructions comprising: generating a key pair that comprises a public key and a private key; transmitting the public key to fetch a license file from a subscription server; receiving license file information that includes header information and at least one symmetric key, the header information including a User Identification and an Epoch Identification, wherein the Epoch Identification defines a time period for which the license file is valid; and decrypting a program based in part on the header information.
 8. The processor of claim 7, generating a key pair is associated with an activation process.
 9. The processor of claim 7, the public key is a Client Encryption key and the private key is a Client Decryption key.
 10. The processor of claim 7, further comprising storing a service key contained in the license file on a client.
 11. The processor of claim 7, decrypting the program is performed at substantially a same time as media is rendered on a display.
 12. The processor of claim 7, the license file comprises an encrypted session key and at least one service.
 13. The apparatus of claim 1, wherein the means for generating the public key and the private key is associated with an activation process.
 14. The apparatus of claim 1, wherein the public key is a Client Encryption key and the private key is a Client Decryption key.
 15. The apparatus of claim 1, wherein the license file comprises an encrypted session key and at least one service key.
 16. The computer-readable medium of claim 4, wherein generating an asymmetric key pair is associated with an activation process.
 17. The computer-readable medium of claim 4, wherein the instructions further comprise: storing a service key contained in the license file on a client.
 18. The computer-readable medium of claim 4, wherein the license file comprises an encrypted session key and at least one service key.
 19. The computer-readable medium of claim 6, wherein the public key is a Client Encryption key and the private key is a Client Decryption key. 